Chemistry Notes: Classification of Matter

Classification of Matter

Mixtures

• Homogeneous: All liquid or solid (e.g., sugar, coffee).
• Heterogeneous: Liquid, solid, or gas (e.g., milk, corn).

Classification Based on Bond Type

• Pure Substances: Elements or Compounds
• Mixtures: Homogeneous or Heterogeneous

Elements

• One type of atom.
• Can exist as atomic metallic, atomic covalent, or atomic non-bonding.

Atomic Metallic

• Held together by metallic bonds.
• Malleable & ductile, lustrous, soft to hard.
• Excellent thermal and electrical conduction.
• Examples: Iron (Fe).

Atomic Covalent

• Atoms held together by covalent bonds.
• Very hard, high melting points.
• Poor thermal and electrical conduction (except graphite).
• Examples: Diamond, Silicon (Si).

Atomic Non-bonding

• Atoms have a stable valence electron configuration (Noble gases).
• Non-reactive, non-flammable.
• Low boiling points.
• Can be ionized to conduct electricity.
• Examples: Neon (Ne), Krypton (Kr).

Diatomic Elements

• Two atoms of the same element bonded together (e.g., $H<em>2$, $O</em>2$).
• Low boiling points (gases).
• Not stable as single atoms.

Compounds

• More than one type of atom.
• Ionic or Molecular Covalent.

Ionic Compounds

• Hard, brittle, high melting points.
• Poor thermal insulation.
• Good conductivity in solution.
• Example: Sodium Chloride (NaCl), Magnesium Oxide (MgO).

Molecular Covalent Compounds

• Dispersion forces, dipole-dipole interactions, hydrogen bonding.
• Low to medium melting points.
• Poor thermal and electrical conduction.
• Examples: Water ($H_2O$), benzene.

Examples of Classification

• Rusty Nail: Heterogeneous Mixture - Fe(s) (Metallic) & $Fe<em>2O</em>3$ (rust).
• White Sugar (Sucrose): Homogeneous Mixture - Molecular Covalent Compound.
• Silicon: Atomic Covalent Element.